Cummins/Onan — Testing SCR Bridge Assembly (CR21)
Testing & diagnosis · SCR bridge CR21
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan DFM
Procedure
- Disconnect wires from SCR bridge unit prior to testing
- Test unit in order shown in Table 3
- Refer to Figure 10 for CR4 and CR5 test circuit
- When test is complete and satisfactory, reconnect unit observing correct wiring hook-up
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- RX10K scale: Infinity; RX1 scale: 6- to 50-Ohms; DC voltmeter reading less than 3 Volts
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.